JPH0327628B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a grain-oriented electrical steel sheet with good glass adhesion and low iron loss, and a method for manufacturing the same. [Prior Art] Grain-oriented electrical steel sheets are used as iron cores in electrical equipment such as transformers and generators, but they must have good magnetic core loss characteristics, good excitation characteristics, and excellent glass coating characteristics. is important. Normally, grain-oriented electrical steel sheets are produced by hot rolling a silicon steel material containing 4% Si or less, annealing the hot rolled sheet as necessary, and then performing one or two cold rolling processes to produce a cold rolled sheet with the final finishing thickness. After decarburizing and annealing,
An annealing separator mainly composed of MgO is applied and final annealing is performed to develop secondary recrystallized grains with a Goss orientation. Impurities such as S and N are then removed and a glass film is formed, followed by a flat surface. It is manufactured through a process of stress relief annealing and insulation coating treatment. By the way, among the magnetic properties of grain-oriented electrical steel sheets, improvements in core loss properties and glass coatings are being studied. For example, J.Appl.Phys.38 shows that in order to lower iron loss, it is effective to reduce the thickness of a grain-oriented electrical steel sheet or to make the crystal grains smaller.
(1967). It is disclosed on pages 1104-1108. However, when the plate thickness becomes thinner than a certain thickness, eddy current loss increases rapidly and iron loss increases. Therefore, there is a limit to the reduction in iron loss due to plate thickness. Furthermore, when the plate thickness becomes thinner, there arises a problem that secondary recrystallization becomes poor. In addition, the grain-oriented electrical steel sheet sufficiently exhibits secondary recrystallization to grow crystal grains with Goss orientation.
Since the excitation characteristics and iron loss characteristics are to be improved, there is a limit to the reduction in iron loss due to grain refinement. Regarding the improvement of glass coatings, for example, see Japanese Patent Application Laid-Open No.
In 71526, grain-oriented electrical steel sheets that have been cold-rolled to the final thickness are pickled to remove 3 g/m2 or ^more of the surface layer before being decarburized and annealed to remove surface deposits and base metal. The surface layer is removed, the decarburization reaction and oxide formation reaction proceed evenly, and after decarburization annealing, an annealing separator is applied, and final annealing is performed to create MgO-SiO ₂ -based insulation with good uniformity and adhesion. It is described that it forms a film. Furthermore, in JP-A-57-101673, after decarburizing and annealing a grain-oriented electrical steel strip that has been cold-rolled to the final thickness, before applying an annealing separator such as MgO, the surface of the steel strip is The oxide film on the surface layer of the steel sheet is removed by 0.5g/ ^m2 grinding or pickling, and then an annealing separator is applied and final annealing is performed to create a glass with good adhesion and a uniform gray appearance. It is described that it forms a film. [Problems to be solved by the invention] Through these efforts, film properties such as adhesion of the glass film have been improved, and magnetic properties have also been improved, but this is not sufficient. However, it is hoped that further study will be conducted in the future to improve these characteristics. In other words, in the method disclosed in JP-A-50-71526, the entire surface layer of the steel plate is removed to a uniform depth by pickling, so a tension effect based on this cannot be expected.
Furthermore, the method disclosed in JP-A-57-101673 has the effect of improving the adhesion of the forsterite film by removing the oxide film on the surface layer of the steel sheet, but
Since the removed amount is not large enough to penetrate into the inside of the base metal, it is not possible to improve the magnetic properties due to the tension effect. The present invention was completed as a result of various experiments and studies with the aim of providing a grain-oriented electrical steel sheet with improved adhesion of the glass coating, enhanced tension effect, and low core loss. [Means for solving the problem] As a result of study, the present inventors found that forming an oxide partially penetrated into the steel plate substrate produces an anchor effect and reduces the adhesion of the glass film. It has been found that a grain-oriented electrical steel sheet with low core loss can be obtained, which has been greatly improved and the tensile effect of the film has also been dramatically improved. This decrease in iron loss is so large that it cannot be considered solely due to an increase in film tension, and it is presumed that the magnetic domains are segmented by the oxide. The present invention will be explained in detail below. The present inventors have discovered that the form of the oxide layer formed on the surface of the steel sheet during decarburization annealing and the form of the glass film formed by the reaction between the oxide layer and the annealing separator affect the adhesion of the glass film, the tension on the steel sheet, and The effect on iron loss was investigated. Hereinafter, formed by such a process,
The layer formed inside the base iron of a steel sheet by any of _SiO2- rich Fe oxide, normal oxide, and oxide containing some forsterite is called an internal oxidation layer.
In this experiment, the surface of a cold-rolled grain-oriented electrical steel sheet cold-rolled to a final thickness of 0.225 mm was polished with sandpaper of different roughness to form sharp and fine irregularities, and then decarburized. Annealing was performed to change the depth and morphology of the internal oxidation layer formed on the steel sheet. Thereafter, an annealing separator containing MgO as a main component was applied and final annealing was performed. As shown in Figure 1B, the internal oxidation layer was formed to a fairly uniform thickness in the unpolished steel plate, whereas in the polished specimen, as shown in Figure 1A, it was partially formed on the steel plate. It was formed deeply by penetrating the inside of the underground railway.
After applying an annealing separator and finishing annealing, the adhesion of the glass film was investigated by bending the glass film by 10 mmφ, which is more severe than the 20 to 50 mmφ bending under normal test conditions, and examining the peeling area ratio, as shown in Figure 2. Samples A and B, which were formed by partially penetrating the layer into the inside of the base metal, exhibited extremely good adhesion without peeling. Furthermore, the tension applied to the steel plate was greatly improved as shown in Figure 3. As shown in Fig. 4, it was found that the iron loss was significantly reduced and that the iron loss could be lowered. In the case where the internal oxidation layer was formed deeply, the glass film was similarly formed deeply during final annealing. The oxide is partially formed inside the base metal of the steel plate at a depth of 5 to 15 μm below the surface of the base metal. Setting the lower limit to 5μm increases the adhesion of the glass film,
Further, in order to achieve the effect of improving iron loss characteristics, a depth of 5 μm or more is required as shown in the examples. On the other hand, if this depth becomes large, magnetic flux density and iron loss deteriorate, so it is set to 15 μm or less. Here, the term "partial" refers to a state in which the oxide is discontinuous or continuous, with protrusions appearing at non-uniform or equal intervals. Next, a method for manufacturing a grain-oriented electrical steel sheet according to the present invention will be described. It is not necessary to specify the steel composition of grain-oriented electrical steel sheet and the manufacturing conditions until cold rolling.
is 0.04 to 0.10%, Si is 2.0 to 4.0%, and appropriate inhibitors such as AlN, MnS, MnSe, BN, Cu ₂ S, etc. are used, and if necessary, Cu, Sn, Cr,
Contains elements such as Ni, Mo, and Sn. An electromagnetic steel slab is hot rolled, annealed, and then cold rolled once or twice or more with intermediate annealing to achieve a desired final thickness. Next, before or after decarburization annealing, the surface of the steel sheet is processed by appropriate mechanical processing means such as brush roll, sandpaper, grinder, shot blasting, etc. so that sharp and fine irregularities are present on the surface of the steel sheet. Activate. By activating the surface of the steel sheet, a thick oxide film rich in SiO ₂ is formed during decarburization annealing or finish annealing. When this SiO ₂ -based oxide film is formed thickly, the glass film formed by the reaction with the annealing separator becomes thick and of good quality. The above-mentioned irregularities are formed on the surface of the steel sheet by locally promoting chemical reactions such as oxidation inside the base steel of the steel sheet during decarburization annealing or finish annealing, and oxides partially penetrate into the inside of the steel base of the steel sheet. This is to form. The sharp and fine irregularities are formed on one or both sides of the steel plate, for example, 35% of the surface area of the steel plate.
% or more. Moreover, the depth of the unevenness is 5 to 15 μm from the surface of the base iron. If the depth of this unevenness is shallow, the penetration depth of the oxide into the steel plate substrate will be insufficient, and it will not be possible to obtain the effect of improving the adhesion of the glass film and the specification of iron loss, so it is necessary to make it 5 μm or more. be. On the other hand, if the unevenness is too deep, the magnetic flux density and iron loss will deteriorate, so 15μ
m or less. The unevenness may be provided in any direction. When performing mechanical processing on the surface of a steel sheet before decarburization annealing, decarburization annealing increases the dew point to promote decarburization and oxidation reactions, for example, at 850℃ with 25% N ₂ +
In the case of an atmosphere containing 75% H ₂ , it is preferable to conduct the reaction at a dew point of 60 to 70°C or higher. After decarburization annealing, MgO is the main component,
An annealing separator containing additives such as TiO ₂ , B compound, SrS, SnS, and CuS is applied, dried, and final annealed. During the final annealing, the annealing separator reacts with the oxide formed during the decarburization annealing, which partially penetrates into the steel plate substrate from the average thickness, to form a glass film. In addition, if the sharp and fine irregularities are formed on the surface of the steel plate after decarburization annealing, the annealing separation material is applied, and then finish annealing is performed, and the finish annealing partially forms the surface of the steel plate. Oxide penetrating into the iron is formed and a glass film is formed. The glass coating has very good adhesion because it is connected to the oxide that is partially deeply penetrated into the base metal of the steel plate, or because it is also partially deeply penetrated. Furthermore, the tension that the coating imparts to the steel sheet is greatly increased, resulting in a steel sheet with extremely low iron loss. Since this decrease in core loss is so remarkable that it cannot be explained by the effect of increasing film tension alone, it is inferred that the magnetic domains are segmented by the formation of the oxide. Thereafter, if necessary, flattening annealing is performed, and the steel plate is treated with phosphoric acid, phosphates such as aluminum phosphate, magnesium phosphate, zinc phosphate, calcium phosphate, etc., chromates such as chromic acid and magnesium chromate, etc. Apply an insulating coating solution containing one or more of dichromate, colloidal silica, etc.
An insulating film is formed by baking at a temperature of 350℃ or higher. [Example] Next, an example will be shown. Example 1 C: 0.065, Si: 3.25, Mn: 0.068 in weight%
A silicon steel slab consisting of Al: 0.027, S: 0.023, Cu: 0.07, Sn: 0.12 balance iron was hot-rolled, annealed and cold-rolled by a well-known method to obtain a 0.250mm thick steel plate. This was used as the sample material. By changing the roughness of the sandpaper on the steel plate, the steel plate surface roughness was 12μm,
Polishing was performed so that the area ratio of the treated portions in which irregularities of 9 μm, 7 μm, 5 μm, and 3 μm were formed was 50%. After carrying out the following steps: decarburization annealing, application of an annealing separator, and final annealing, the film properties and magnetic properties of the finished plate, which had been coated with an insulating coating and subjected to heat flattening, were measured. The results are shown in Table 1. In addition, in the investigation of film adhesion, since all of the films, including the "untreated" material, did not peel and were good under normal bending conditions of 20 to 50 mmφ, tests were carried out under even more severe bending conditions of 10 mmφ.

[Table] Example 2 C: 0.060, Si: 3.15, Mn: 0.070, in weight%
Al: 0.030, S: 0.024, Cu: 0.07, Sn: 0.13%,
A silicon steel slab consisting of the remainder iron was treated and cold rolled in the same manner as in Example 1 to obtain a 0.29 mm thick steel plate. The steel plate is blasted to a depth of 25 to 10μ by square shot blasting.
The treatment was performed so that the area ratio of the shot treated portion was 80% or more with an unevenness of m. Next, after carrying out the steps of decarburization annealing, application of an annealing separator, and final annealing, the film properties and magnetic properties of the finished plate, which was subjected to application of an insulating coating and heat flattening, were investigated. The result is the second
Shown in the table.

[Table] Example 3 Weight %: C: 0.058, Si: 3.10, Mn: 0.065,
A silicon steel slab consisting of Al: 0.0010, S: 0.024 and the balance iron was cold-rolled twice by a well-known method to obtain a steel plate with a thickness of 0.265 mm, which was used as a "before treatment" test material.
The surface roughness of the steel plate is 3 to 4μ with a brush roll.
Polishing was carried out so that the area ratio of the surface of the steel plate having irregularities of m, 5 to 6 μm, 8 to 10 μm, and 12 to 15 μm was approximately 70%. Next, the following steps of decarburization annealing, application of an annealing separation agent, and final annealing were carried out, and then the coating properties and magnetic properties of the finished plate, which had been subjected to application of an insulating coating and heat flattening, were measured. We also measured the tension of the glass film before insulating coating treatment. The results are shown in Table 3.

[Table] Example 4 A cold-rolled plate with a thickness of 0.225 mm prepared in the same manner as in Example 1 was heated at 850°C in a humid atmosphere of 25% N ₂ + 75% H ₂
The specimen was decarburized and annealed for 3 minutes. This decarburized plate is processed with a brush roll to a steel plate surface roughness of 12 to 15μ, 8
Polishing was performed so that the area ratio of the treated portions at depths of ~10μ, 4~6μ, and 2~3μ was approximately 50%. Next, after applying an annealing separator, final annealing was performed at 1200°C for 20 hours, and the magnetic properties of the finished plate, which had been coated with an insulating coating and subjected to heat flattening, were measured. The results are shown in Table 4.

[Table] (Effects of the Invention) As recognized from the above examples, according to the present invention, a grain-oriented electrical steel sheet with excellent film adhesion and extremely low core loss can be obtained.

[Brief explanation of the drawing]

Figures 1A and B are metallurgical microscopic photographs showing examples of internal oxidation layers formed on the surface layer of steel plates according to the present invention and comparative examples, and Figure 2 is the impact depth of the internal oxide layer on the adhesion of the glass film. Figure 3 is a diagram showing the effect of the penetration depth of the internal oxide layer on the tension on the steel plate, and Figure 4 is a diagram showing the effect of the penetration depth of the internal oxide layer on iron loss. It is.

Claims (1)

[Claims] 1. In a grain-oriented electrical steel sheet on which a glass film is formed, an oxide is present at a distance of 5 to 15 μm from the base steel surface of the steel sheet.
A grain-oriented electrical steel sheet with good adhesion of a glass film and low iron loss, characterized by a partially sharp shape formed at a depth of 35% or more of the surface of the steel sheet. 2 A directional electromagnetic method in which a silicon steel slab is hot rolled, annealed, cold rolled once or twice or more with intermediate annealing, decarburized annealed, coated with an annealing separator, and then finish annealed. In the method for manufacturing a steel plate, the surface of the steel plate is subjected to mechanical processing before or after the decarburization annealing to form sharp and fine irregularities on the surface of the steel plate at a depth of 5 to 15 μm from the base surface of the steel plate, and the steel plate is A glass characterized in that oxides are formed partially over 35% or more of the surface, and then the steel sheet is subjected to the decarburization annealing or finish annealing to form oxides on the uneven portions of the surface of the steel sheet. A method for manufacturing a grain-oriented electrical steel sheet with good film adhesion and low core loss.